Speaker
Description
We study the two step sequential one pion production mechanism, np(I=0)→π−pp, followed by the fusion reaction pp→π+d, in order to describe the np→π+π−d reaction with π+π− in I=0, where a narrow peak, so far identified with a "d(2380)" dibaryon, has been observed. We find that the second step pp→π+d is driven by a triangle singularity that determines the position of the peak of the reaction and the large strength of the cross section. The combined cross section of these two mechanisms produce a narrow peak with the position, width and strength compatible with the experimental observation within the approximations done. This novel interpretation of the peak without invoking a dibaryon explains why the peak is not observed in other reactions where it has been searched for.
